Refine comment and division operator lex logic

This removes original unreachable error branch on '/' tokenization, and
also adds C++-style comment (which is introduced in C99 specification)
support. Additionally, the C-style comment is refined with proper
detection on unenclosed case.

Author: ChAoSUnItY

src/lexer.c

@@ -216,9 +216,10 @@ token_t lex_token_internal(bool aliasing)
         error("Unknown directive");
     }
 
-    /* C-style comments */
     if (next_char == '/') {
-        read_char(false);
+        read_char(true);
+
+        /* C-style comments */
         if (next_char == '*') {
             /* in a comment, skip until end */
             do {
@@ -231,14 +232,21 @@ token_t lex_token_internal(bool aliasing)
                     }
                 }
             } while (next_char);
-        } else {
-            /* single '/', predict divide */
-            if (next_char == ' ')
-                read_char(true);
-            return T_divide;
+
+            if (!next_char)
+                error("Unenclosed C-style comment");
+            return lex_token_internal(aliasing);
         }
-        /* TODO: check invalid cases */
-        error("Unexpected '/'");
+
+        /* C++-style comments */
+        if (next_char == '/') {
+            do {
+                read_char(false);
+            } while (next_char && !is_newline(next_char));
+            return lex_token_internal(aliasing);
+        }
+
+        return T_divide;
     }
 
     if (is_digit(next_char)) {

tests/driver.sh

@@ -233,6 +233,39 @@ items 0 "int x; for(x = 10; x > 0; x--); return x;"
 items 30 "int i; int acc; i = 0; acc = 0; do { i = i + 1; if (i - 1 < 5) continue; acc = acc + i; if (i == 9) break; } while (i < 10); return acc;"
 items 26 "int acc; acc = 0; int i; for (i = 0; i < 100; i++) { if (i < 5) continue; if (i == 9) break; acc = acc + i; } return acc;"
 
+# C-style comments / C++-style comments
+# Start
+try_ 0 << EOF
+/* This is a test C-style comments */
+int main() { return 0; }
+EOF
+try_ 0 << EOF
+// This is a test C++-style comments
+int main() { return 0; }
+EOF
+# Middle
+try_ 0 << EOF
+int main() {
+    /* This is a test C-style comments */
+    return 0;
+}
+EOF
+try_ 0 << EOF
+int main() {
+    // This is a test C++-style comments
+    return 0;
+}
+EOF
+# End
+try_ 0 << EOF
+int main() { return 0; }
+/* This is a test C-style comments */
+EOF
+try_ 0 << EOF
+int main() { return 0; }
+// This is a test C++-style comments
+EOF
+
 # functions
 try_ 55 << EOF
 int sum(int m, int n) {